This application is related to the concurrently filed Angarola et al. applications, Ser. Nos. 820,163 and 820,162, entitled, respectively, "Dunnage Bag Fill Valve", and "Apparatus for Rapidly Inflating and Pressurizing a Dunnage Bag", and U.S. Pat. No. 4,102,364 Leslie et al. entitled "Method of Dunnage Bag Inflation".
This invention relates to dunnage bags for use in shipment of freight by rail, ship, truck, aircraft and the like, and more particularly to inflatable disposable dunnage bags for such use. Typically, such dunnage bags have a gas-tight bladder (usually polyethylene) surrounded by an outer protective and supportive shroud consisting of a number of plies of heavy paper. The inflatable, disposable dunnage bags are used in freight carriers where it is customary to fill the spaces between the cargo, or between the cargo and the walls of the freight carrier, to prevent the cargo from shifting and damaging either the cargo itself and/or the walls of the freight carrier. Inflatable, disposable dunnage bags are placed between the cargo in a deflated condition and are subsequently inflated with a gas, usually air, to a certain design pressure, typically between 1 and 8 pounds per square inch gauge, dependent on the size and wall structure of the particular bag.
Experience with this type of dunnage bag has revealed certain difficulties during inflation. First, in the United States, such dunnage bags are normally inflated with high pressure air nozzles through a valve in the side of the bag. Typically, the high pressure air ranges between 30 and 120 pounds per square inch gauge. Thus, unless the air pressure is carefully regulated (as by means of a pressure regulating device near the discharge of the air hose), it is quite easy to pressurize a bag beyond the design, or allowable, pressure limit and to thereby rupture the bag and possibly damage the cargo and/or carrier. Thus, it would be desirable to provide a means for filling such dunnage bags using a gas such as air without the danger of overpressurization.
It has been suggested that low pressure air could be used. However, the use of low pressure air, by itself, has a number of drawbacks. First, the time required to fill a dunnage bag would typically be longer than the time required to fill a dunnage bag when using high pressure air. Also, a dunnage bag can still be overpressurized and ruptured when using low pressure air unless the particular "low" pressure is adjusted low enough for the particular dunnage bag. This may damage the cargo. Thus, in situations where a number of different sizes of dunnage bags (having different design fill pressures) are to be inflated with the same low pressure air supply, the low pressure air supply pressure would still have to be carefully regulated to accommodate each different bag being filled. To overcome these drawbacks, it would be desirable to provide a means for filling different design pressure dunnage bags with low pressure air relatively rapidly and yet also have an automatic self-limiting feature with respect to the maximum pressure which could be supplied to a particular bag. Specifically, it would be desirable to provide a dunnage bag filling device which could be used with various sizes of dunnage bags having various different maximum allowable fill pressures and which, when operated from a given constant air supply pressure in cooperation with the particular valve on each of the various dunnage bags, would permit filling of the dunnage bags to, but not in excess of, their respective allowable design pressure levels.
Another problem encountered with the filling of inflatable dunnage bags results from the fact that such bags are filled after they have been placed and positioned between cargo or between the walls of the freight carrier and the cargo. Consequently, there are many times when access to the fill valve on the dunnage bag is extremely limited. In those instances, there is very little clearance area around a fill valve and this precludes the use of large, elongated gun-type air injection mechanisms that stick out a number of inches from the top of the valve during inflation. Consequently, it would be desirable to provide an air injection device which could be mounted on the dunnage bag fill valve and which would project only a relatively short distance from the top of the valve.